“The shark did not look like it had been visibly wounded,” Dearth said. “An officer found it in the tide area.”

John Mandelman, senior scientist at the New England Aquarium, said the cause of death cannot be confirmed.

However, he said the animal most likely died after being caught and released by a fisherman, or because of an infection or some other natural cause.

Judging by the size of the shark, Mandelman said, it appeared to be a juvenile, as adult female blue sharks can grow more than 10 feet long. With the tide coming in, police left the shark on the beach overnight in hopes the tide would take it back out into the ocean.

“Blue sharks are incredibly common in our coastal and offshore waters . . . and dead specimens often wash up on shore,” Mandelman said in an e-mail. “The occurrence of this specimen certainly doesn’t signal a possible threat to human safety.”

The aquarium was not involved, and Mandelman identified the species based on a photo provided by police.